Aspects of the extension of forty exploitation of bulk reservoirs for irrigation and hydropower purposes

2 Research methodology
For studying and analyzing the current channel processes, materials from field studies to 
determine the decrease in the useful volume of the reservoirs [1] of irrigation and 
hydropower purposes and the results of studies conducted on a specific object [5, 6] - the 
supply channel of Aktepe reservoir were used. The territory of Aktepe reservoir is located 
on the left bank of the Surkhandarya River, 30 km north of the city of Termez, and is a 
depression extending from north to south, 7–7.5 km long, 3–4 km wide. From the west it is 
bounded by the Amu-Zang and Kokaity canals, from the north and east by the foothills of 
the Ak-Tau range. 
The slope of the groundwater mirror I = 0.01 in some areas increases to 0.05. The end 
section of the trapezoidal feed channel in a concrete lining, 2 km long, with zigzag ribs of 
artificial roughness. The channel is designed to pass 25 m3 / s. [5,6] 
3 Research and discussion results 
Due to the high saturation of the flow, the silting dynamics of the reservoirs entering the 
reservoir thicket is of an intensive nature (Table 1). 
Table 1. 
№ 
Name of bulk 
reservoirs 
Water 
abstraction 
Gross 
capacity, 
mln.м
3
Operati
ng 
period 
Silting 
dynamics 
during the 
operating 
period 
Silting 
capacity 
1 
Akdaryo 
Akdarya 
112.5 
20 
93.17 
17,18222 
2 
Andijan 
Kharadarya 
1900 
20 
1664.8 
12,37895 
3 
Akhangaran 
Akhangaran 
210.36 
24 
200.16 
4,848831 
4 
Jizzax 
Sanzor 
100 
30 
80.08 
19,92000 
5 
Kattakurgan 
Zarafshan 
900 
35 
697.46 
22,50444 
2
E3S Web of Conferences 97, 05008 (2019)
https://doi.org/10.1051/e3sconf/20199705008
FORM-2019

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6 
South Surkhan 
Surkhandarya 
800 
35 
503 
37,12500 
7 
Quemazar 
Amudarya, 
Zarafshan 
310 
42 
274.5 
11,45161 
8 
Pachkama 
Guzardarya 
260 
36 
192.6 
25,92308 
9 
Talimarjan 
КМК, 
Amudarya 
1525 
17 
1464.03 
3,998033 
10 
Tashkent 
Angren 
250 
37 
207.68 
16,92800 
11 
Tudakul 
АBМК, 
Zarafshan 
1200 
33 
1035.4 
13,71667 
12 
Tupalang 
Tupalang 
100 
20 
83.35 
16,65000 
13 
Aktepe 
Amudarya 
100 
13 
89,27 
9,730000 
It should be noted that only suspended sediments transported by water flow from the river 
enter the bulk reservoirs and they can often flow through the reservoir along with the 
stream, and if we take into account the fact that during the filling of the bulk reservoirs 
(during the winter months and before the growing season) the average turbidity of the rivers 
of Central Asia) is the minimum value (0.5-4 kg/m
3
), then it can be determined that the 
reservoirs will be silted annually by 0.002-0.004 part of the useful capacity of the reservoir 
for their full siltation the storage will take several hundred years [1,7,8]. Usually, in many 
rivers, measures ensuring the prevention of the flow of bottom and coarse sediment 
fractions are carried out at the head water intake structure on the river and they, as a rule, 
do not enter the reservoirs. On the rise of the flood, when the flow carries the greatest 
amount of sediment and at the same time the flow of the river is still small, it is possible to 
regulate the volume of water supplied to the bulk reservoirs, thereby reducing the volume 
of their sedimentation [9,10]. 
As shown by the results of research in the reservoirs of the Amudarya and Syrdarya 
river basins, the design period for the sedimentation of the dead volume of these reservoirs 
varies from 34 to 126 years and the silting period for the total volume of the reservoir is 
more than 700 years. The average value of the annual loss of the capacity of the bulk 
reservoirs is 0.11%, therefore, the sedimentation of such reservoirs mainly occurs only at 
the expense of mudflows. The annual solid flow of such rivers is 0.03 - 0.7% of the 
reservoir capacity, i.e. their full silting will occur after 150–1000 years of operation of the 
reservoir [3,7]. 
Analysis of the operational services data, following the course of re-formation of the 
channel at the dams of the channel reservoirs located in our state with a capacity of more 
than 50 million m3, from the beginning of their operation to the present time showed that 
the main factor in reducing the useful volume of the reservoir is the deformation of the 
channel of the reservoir. This is due to the sedimentation of sediment entering the reservoir 
along with the stream. As a result of a sharp expansion of the channel in the inlet, the 
average velocity decreases, which leads to a decrease in the transporting capacity of the 
stream, contributing to the beginning of the silting process. The actual volume of sediment 
deposited in the reservoir always exceeds the design volume, (Table No. 2):